System for translating a d. c. component



A. J. DE vRlEs 2,910,527

4 Sheets-Sheet 1 SYSTEM FOR TRANSLATING A D.C. COMPONENT Oct. 27, 1959Filed June 7. 1955 4 Sheets--Sheaetl 2 IN VEN TOR.

HIS ATTORNEY.

06h 27, 1959 A. J. DE vRlz-:s

SYSTEM FOR TRANSLATING A D.C. COMPONENT Filed June 7, 1955 ADRIAN J.DEVRIES yawn# Oct. 27, 1959 A. J. DE VRIES SYSTEM FOR TRANSLATING A D.C.COMPONENT Filed June 7. 1955 4 Sheets-Sheet 3 Flo. 3

lnmmnnnnmn DRIAN J. DEVRIES INVENTOR.

@2M/ef HIS ATTORNEY.

Oct. 27, 1959 A. J. DE vRlEs 2,910,527

SYSTEM FOR TRANSLATING A D C. COMPONENT Filed June 7. 1955 4Sheets-Sheet 4 .||||||...|||||....|||I|. mln..o

Time- FIG. 4

ADR|AN J. DEVRIES INVENTOR.

HIS ATTORNEY.

' changes.

nited States Pat A 4,910,527 Y SYSTEM non rRANsLArrNG A no.v coMPoNENrAdrian J. De Vries, Oak Park, Ill., assigner to Zenith RadioCorporation, incorporation of Delaware Application June 7, 195s, serialNd, 513,868 s claims. (c1. r17in-5.1)

currently herewith, andy issued February 3, 1959, as Patent Y 2,872,507,in the name of Walter S. Druz, and assigned to the present assignee,"an-arrangement is disclosed for transmitting and reproducing the D.C.component as well as the A.C. component of anr audio signal which hasbeen coded by altering some characteristic thereof, Vsuch as phase. Likethe present case,the Druz arrangement Y 2,910,527 Patented Oct. 27,1959

ice

Serial No. 397,176, filed December 9, 1953, in the name of Howard K. VanJ epmond, and assigned-to thejpresentV assignee. The operation ofthesampler may be so phased with respect to the decoding process that thedecoded signal is only sampled at times other than the instants of phaseinversion.

a sampled only during those` intervals when no distortion .t transientsare present.

avoids the distortion otherwise'introduced during theV decoding processwhen the D.C.` component is not conveyed. Briey, the D.C. component isamplitude modulated on a sub-carrier at the transmitter, preferably in asuppressed carrier type modulator, and then both the A.C. component andthe D.C. modulated sub-carrier are frequency modulated on a maincarrierfor transmission to a receiver. There the main kcarrier Wave isfirst demodulated to recover the A.C. component and the D.C. modulatedsub-carrier and subsequently the D.C. component is derived by means of asecond demodulator,` such as a synchronous detector. -The A.C. and D.C.components are then both employed in the decoding process pto develop asignal Which corresponds to the original uncoded audio signal. Y,

In addition to the type distortion attributable to the loss of the D.C.componentand which may be eliminated with the Druz arrangement, there isstill another type of distortion that may result from the coding:process. This distortion maybe charged, inter alia, to the limited bandwidth allotted to audio transmission which prevents the translation ofthe entire range of frequency components representing the extremelysharp amplitude excursions of the coded audio signal produced by thephase inversion of the coding operation; almost an infinite band widthwould actually be required to duplicate such abrupt Consequently, it isdiiicult in electing compensating phase inversions in the decodingprocess at the receiver to 'avoid transient distortion pulses. Moreover,the compensating phase changes in the decoding apparatus at the receiverdo not always occur in exact time coincidence with the correspondingphase changes at the transmitter. Additional undesirable transientpulses are consequently generated and reflected as transient distortionin the decoded audio signal.

Transient distortion of this type occurs essentially at the instants ofphase inversion in the decoding process and may be effectively removedby interposing a sampling circuit andV a low-pass ilter in the audiochannel in accordance with the teachings of copending application tionof the original signal.

The present invention stems from the previous Work of Druz and VanIepmond and provides a receiver that` achieves essentially the sameresults as both prior systems except that a considerably simpler andlessV expensive arrangement is used. Y

l It is, accordingly, an 'object of the present invention to provide animproved and inexpensive D;C. translating system of the type disclosedin the Druzv application.

It is another object ofthe invention to provide a simplitied circuit forsimultaneously achieving the results of both the Druz and the Van.lepmond systems.

It is stilll another object of the present invention to provide a novelarrangement for translating a D VC. or very low frequency component ofan intelligence signal.

It is still another object torprovide a receiver for utilizing a'complexmodulatedmain carrier wave having one modulation component comprising asub-carrier signal representing the D.C. component of an intelligencesignal and another modulation component representing the A.C. componentof the same intelligence signal.

It is a still further object of the present invention to provide areceiver for utilizing a modulated main carrier wave representingv anaudio signal which has been sub jected to a phase-inversion type ofcoding process andV converted into a coded audio signal having an A.C.component and a,D.C. component which components are individuallyrepresented by separate modulations of a main' carrier wave.

A receiver, in accordance with one aspect Vof the invention, utilizes acomplex modulated main carrier wave having one modulation componentcomprising a subcarrier signal representing'the D.C. component of anintelligence signal conveying certain information andr anothermodulation component representing the A.C. component of the intelligencesignal. The receiver includes demodulating means for demodulating themain carrier wave to produce a complex wave form consisting of thesub-carrier signal and the A.C. component superimposed on each other.Means coupled to the demoulating means phase inverts spaced portions ofthe complex wave form to develop a composite signal containing thesub-carrier signal as a component thereof. Sampling means is providedfor effectively sampling the composite signal only at predeterminedphase conditions of the subcarrier component to develop an output signalconsisting of the sampled portions. Finally, the receiver includesfrequency selective means for shaping the Wave form` of the outputsignal to form a signal simulating the intelligence signal information.

The features of this invention which are believed to be new are setforth with particularity in the appended claims'.

The invention itself, together with further objects and advantagesthereof, may best be understood, however,

by reference to the following description when taken in` conjunctionwith the accompanying drawings, in which:

Figure l is a schematic representation of a subscription` by asub-carrier which has previously been modulated' by the DtC. componentof thesame coded audio signal;

In this way, the decoded signal is The sampled signal is then shaped inthe low-pass lter producing a distortion-free simula- Figure 2 is aschematic representation of a subscription television receiverconstructed in accordance with the invention to utilize the main carrierwave developed in the transmitter ofFigure 1; yand Figures 3 and 4,taken together with Figure 4 placed immediately below Figure 3,constitute a family of curves used in explaining the operation of thesystem.

The transmitter of Figure 1 includes a picture-converting or pick-updevice 12 lwhich may be of any wellknown construction for deriving avideo signal representing the image to be televised. The outputterminals of device 12 are connected through a video amplifier 13 and avideo coder 14 to one pair of input terminals of amixer amplifier 15.Video co'der 14 maybe similar to thatrdisclosed and claimed in copendingapplication Serial No. 243,039, filexl August 22, 1951, issued August 7,1956, as Patent 2,758,153, in the name of Robert Adler, and assignedtothe present assignee. Coder 14 may comprise a beam-deflection tubehaving a pair of output circuits -which may be selectively coupled intothe video channel as the electron Vbeam is deflected from one to theother of two Vtarget anodes coupled to such output circuits. One ofthese circuits includes a timedelay network so that the timing of thevideo components relative to the synchronizing components of theradiated signal varies as the beam of the deflection tube is switchedbetween its anodes. This switching eifect is mixer 31 to supply theretothe 31.5 kilocycle sub-carrier wave amplitude modulated by the D.C.component of the coded audio signal. The output circuit of mixer 31 isconnected through an audio carrier wave generator and A A modulator 36.to, another input circuit of Vdiplexer 18.

accomplished by means of a beam deiiection-control or Y actuating signalapplied to video coder 14, as explained hereinafter. Such intermittentvariations in the relative timing of the video and synchronizingcomponents effectively codes the picture information since conventionaltelevision receivers, not equipped with suitable Video decodingapparatus, depend upon an invariant time relation ofthe video andsynchronizing components of a received signal to reproduce the imageintelligence represented thereby.

Mixer amplifier 15 Vis coupled through a direct current inserter 16 to avideo carrier wave generator and modulatoi- 17 which, in turn, isconnected through a diplexer 18 to an antenna 19. The transmitter alsoincludes a synchronizing-signal generator 20 which supplies the usuallineand field-synchronizing components and associated pedestalcomponents to mixer 15. Generator 20 further supplies eldand line-drivepulses to a fieldsweep system'21 and to a line-sweep system 22,respectively. The output terminals of sweep systems 21 and 22 areconnected respectively to the field-and line-deflection elements (notshown) associated with picture-converting device 12.

A microphone 24 is connected through an audio amplifier 25 to the inputterminals of a phase splitter 26 which has a balanced output circuitsupplying signals in push-pull relation to input circuits of anelectronic switch iaudio coder28. Switch 28 may be conventional inconstruction or may be as described and claimed in copending applicationSerial No. 440,224, led June 29, .1954, and issued April 14, 1959, asPatent 2,882,398, 1n the name of Robert Adler, and assigned to thepresent assignee; it operates under the control of an applied squarewave coding signal to alternately translate the audio signal to itsoutput circuit with no phase change and with a phase inversion. A codedaudio signal is developed in coder 28 which at times has a D.C. or verylow frequency component.

Coder 28 is connected to one input circuit of an adder or mixer v31 andhas a series-connected resistor 29 and a condenser coupled across itsoutput terminals. Condenser 30 establishes a charge potentialcorresponding to the D.C. component of the coded audio signal and thispotential is impressed, as a modulating signal, on an auxiliarysuppressed carrier, amplitude modulator 32 by virtue of -aconnectionfrorn the junction of resistor 29 and condenser 30 to oneinput circuit of the modulator. A sub-carrier oscillator 34 has itssynchronizing ifuit Prefenably, the time constant of the circuits fromwhich the D.C. modulated sub-carrier is derived is matched or madecomplementary to the time constant of the entire translating channel forthe coded A C. components from coder 28' at the transmitter to acorresponding decoder at the receiver; otherwise the rate of change ofthe D.C. component will be incorrect and proper compensation will not beachieved.

A coding signal source 3S supplies a square Wave coding signal to audiocoder 28 4and also, as a deflection-control signal, to the deflectionelectrodes of video coder 14 in order to realize both sound and picturecoding. The manner in which the coding signal is developed andinformation concerning its phase or other significant characteristicis.conveyed to subscriber receivers is entirely immaterialto the presentinvention. Copending application Serial No. 366,727, tiled July 8, 1953,and issued September 16, 1958, as Patent 2,852,598, in the name of ErwinM. Roschke, and assigned to the present assignee, shows one codingsignal source suitable for use as unit 38. Briefly, a counting deviceresponds to linesynchronizing pulses to develop a square wave signalhaving iamplitude changes occurring during the line-retrace intervalfollowing each succession of 15 line-trace intervals. During thefield-retrace intervals coding pulses are developed and supplied tovarious input circuits of a bi-stable multivibrator to effect actuationthereof, preferably in random fashion. The counting device is rephasedduring each field-retrace interval under the control of the bi-stablemultivibrator and thus the square wave coding signal from the counter isphasemodulated in a randommanner. The code signal pulses may betransmitted along with the video signal during the field-retraceintervals to facilitate the proper phasing of asimilar square-wavegenerator at the receiver.

In the operation of the described transmitter, pictureconverting device12 produces a video signal representing the program information yto betelevised and this signal, after amplification in video amplifier 13, issupplied through video coder 14 tormixer amplier 15. Meanwhile, codingsignal source 38 develops a square wave coding signal employed `as adeflection-control signal for video coder 14 in order elfectively tovarythe time relationship between the video components and thesynchronizing components of the radiated signal -as disclosed in detailin the aforementioned Roschke application.

Mixer amplier 15 `also receives the usual lineand eldsynchronizing andblanking pulses from generator 20 so that a coded compositeftelevisionsignal Iis developed therein. That signal is adjusted-as to backgroundlevel in direct current inserter 16 and is amplitude modulated on apicture carrier in unit 17. The modulated video carrier is suppliedthrough diplexer 18 to antenna 19 for transmission Yto subscriberreceivers. It will, of course, be understood that in the generation ofthe video components, sweep systems 21 and 22 are synchronized by theeld- `and line-drive pulses applied thereto by generator 20.

The audio information accompanying the video information is picked up bymicrophone 24 and supplied to audio amplifier 25; phase splitter 26receives the audio signal from amplifier 25 and supplies it in push-pullrelation t9 unit 28 wherein audio coding ltakes place.

audio signal.

In order to simplify a detailed explanation of the audio coding process,idealized signal Wave forms which appear at cerain points within theaudio section indicated by encircled-reference letters are identified bycorresponding designations in Figures 3 and-4.'v It Will be rememberedthat Figure 4 should be placed immediately below Figure 3. Assume' thatthe coding square wave signal from source 38A has a frequency ofapproximately cycles per second and thatthe representative audio signalof curve A is of the same frequency. The signals of curves A and Arepresent .the output of phase splitter Z6 which is applied, push pull,to audio coder 28. Assume further that the amplitude changes or ex= 1Vcursions ofthe coding square Wave-occur during certain line-retraceintervals and also substantially in time coincidence with ,the zerocross-over points of the signals of curves A and A', as shown-by curveB.v Audio coder 28, in response to the coding square wave, translatesonly selected half cycles of the signals. of curves A and A', forexample the positive :half cycles, to' its output circuit to' developtherefrom the 'output signal of curve C. Each time a portion of thesignal of curve A-is se# lectedthe transmitter may -be said -to beestablished in mode A operation, Whereas each time a part ofthe signalof curve A is chosen byswitch 28 the transmitter may -be considered tobe in mode B. The time intervals of curve B have been labeledaccordingly.-

The signal of curve C isthe codedaudio and, as may be demonstrated by aFourier analysis, has a D.C. term or component indicated by the dashedconstruction line 78.l Condenser 30 in the output of the audio codercharges to the potential level of dashed line 7 8 in curve C and thispotential is employed to amplitude modulate the 31.5 kilocyclesub-carrier in modulator 32. The D.C. modulatedrsub-carrier is shown incurve D.- Of course, the scaler relationship of 31.5 kilocycles to 500cycles has not been adhered to incurve D yfor convenience ofillustration. For reasons which will become -apparent generator 34 .isso phased that a selected one of the amplitude peaks, for example thepositive peak, of each cycle of the sub-carrier shown in curve D neveroccurs during- -a line-retrace interval.- This may be noted particularlyby observing the instantaneous amplitude of the sub-carrier of curve Dat the instant the amplitude variations of curve B take place, whichofcourse isduring: selected line-retrace intervals;

The D.C. modulated sub-carrier of curve D is combined with the A.C.--componentof the coded audio in adder 31 to develop the' complex waveform of curve E which, in turn, is frequency modulated on the main soundcarrier in unit 36 and applied through diplexer 13 to antenna 19 fromwhich it is concurrently radiated with the modulated `video carrier.Thus, the coded audio signal -is represented by a modulated main soundcarrier wave havingone modulation component comprising a sub-carriersignal representing the D.C. componentof the coded audio signal andanother modulation component representing the A.C. component of thecoded In thismanner all components of the coded signal necessary torecover the original aud-ioat the receiver, in a manner to be explained,are included in the transmission.

' The receiver of Figure 2 is constructedin accordancewith the inventionto decode especially the coded audio signal radiated` by the transmitterof Figure l. It comprises a radiofrequency amplifier 50 which has inputterminals: connected to an antenna 51 and output terminals connected toa tirst.- detector 52. Detector SZ is connected to anintermediate-frequency amplifier 5,3 which,- in turn, is connected to asecond detector 54 having output terminals connected to -avideoamplifier 55. VAmplifier 55 is connected through avideof decoder 56 tothe input electrodes of a cathode-rayl image-reproducing device57. Videodecoder 56- may be similar to video coder 14- at the transmitter exceptthat it is controlled to operate in a complementary `fashion in orderthrough a discrimiator-detector or demodulator 62 to anV audio amplier63. The output circuit of audio ampliiier 63 is connected toa phasesplitter 68 which has a balanced output circuit connected to respectiveinput circuits of an electronic switch audio decoder 69 to supply thecoded audio signal, including the A.C. component and the D.C. modulatedsub-carrier, to decoder 69 with two different phase conditions, apart.Decoder -69 may be identical in construction to coder V28 at thetransmitter so that When actuated by a corresponding control or codinglsignal it el'iects compensating phase inversions of the complex waveform including the A.C. component and the sub-carrier in timecoincidence with the phase inversions at the transmitter. De-f coder 69is connected to one pair of input terminals of a sampling device 70which may be of any Well-.known construction. For example, sampler 70may take either form of the sampling circuits shown in detail in theaforementioned Van Jepmond application. Line-drive pulses are derivedfrom line-sweep system 60 and -applied to a pulse generator 72 which, inturn, is connected to another input circuit of sampling device 70 tosupply a 31.5 kilocycle pulse signal thereto, -in orde'r to effectsampling of a composite signal developed in the output of decoder 69.The output circuit of sampler 7) is coupled through afrequency-selective means, suchv as a suitable low-pass lter 73, to theinput terminals of a speaker 74.

A decoding signa-l source 38', similar to unit 38 of th transmitter, isconnected to audio decoder 69 and to video decoder 56 to provide asquare wave control signal identical to that supplied to thecorresponding .circuits at theV transmitter. The square wave signaldeveloped in unit 38' may be synchronized and phased' with relation tothe coding square wave of the transmitter by means of'signalbursts-transmitted along with the television signal duringvertical-retrace intervals, as is de# scribed in the aforementionedRoschke application, Serial No. 366,727. The phase-modulated square wavefrom source 38' eiects operation of decoder 69 during lineretraceintervals in order to realize compensating phase inversions of the codedaudio' during such intervals. Transient distortion may arise duringphase inversion or mode changing times and, consequently, it isimperative to sample the composite signal developedv in the output ofdecoder 69 at other than mode changing times if the technique ofsampling is to be relied upon to sup`- press transient distortion. Forthis reason, the sub-carrier signal is so phased with respect totheline-drive pulsesV at the transmitter that the positive peak of eachcycle of the sub-carrier" never occurs during a line-retrace interval.Generator 72 may then likewise be so phased with respect to theline-drive pulses at the receiver that the pulses developed for samplingindividually occur in time coincidence with the peaksof the sub-carriercompo-nent in the composite signal developed in decoder 69 thatcorrespond to the positive peaks at the transmitter. s In the operationof the described receiver the coded Vtelevision signal-,is interceptedby antenna 5l, -anipliiied is amplified in intermediate-frequencyamplifier 53 and detected in second detector`54 to produce the codedcomposite video signal. This latter signal is amplified in videoamplifier 55, translated through video decoder 56, and impressed on theinput electrodes of image reproducer 57 to control the intensity of thecathode-ray beam of the reproducing device in Well-'known manner. Videodecoder 56 receives a decoding signal fromsource 38 which has amplitudevariations occurring during lineretrace intervals in exact timecoincidence with,'bu t or. positein phase to, amplitude excursions ofthecoding signal applied as a deection-controlsignal'tothe video coderin the transmitter so that the videocomponents applied to the inputelectrodes of image reproducer 57 are suitably compensated or'decoded toeffect intelligible image reproduction. Y

The synchronizing components of the received signal are separated inseparator 58, the field-synchronizing components being utilized tosynchronize sweep system 59 and, therefore, the field scansion of Vtheimage reproducer while the line-synchronizing pulses are utilized tosynchronize sweep system A60 and, therefore, the line scansion of device57. y

An intercarrier sound signal, which is themainV sound carrier, isdeveloped in detector 54 and separated from the'video in amplifier 55 inaccordance with intercarrier sound principles. The intercarrier signalis amplified and amplitude limited in unit 61, detected in demodulatoror discriminator detector 62, land amplified in audio arnplifier 63 todevelop the complex wave form lof curve E which, of course, is the sameas the signal developed in the output of mixer 31 at the transmitter.The complex wave form of curve E, which contains the 'A,C. component ofthe coded audio signal and also" the subcarrier signal which has beenmodulated bythe component of the coded audio signal, is applied to phasesplitter 68 which translates the applied signal to its two output loadssimultaneously and with opposing phases. Therefore, the signals ofcurves E fand E' are developed by phase splitter 68 for application tothe input circuits of decoder 69.

Decoder 69 operates in time coincidence withv coder 28 at thetransmitter, `and in response to the decoding signal from source 38',and develops in alternation selected portions of curves E and E' in itsoutput circuit. The cornposite signal developed at the output terminalsof decoder 69 is shown in curve F; the composite signal is derived fromthe signal of curve E during mode A intervals when the control signal ofcurve B is positive and is derived from the signal of curve E duringmode B intervals when the control signal of curve B is negative.

From -a close study of the composite W'ave form of curve F it may beobserved that the positive amplitude peaks of the sub-carrier duringmode A intervals and the negative amplitude peaks of the sub-carrierduring mode B intervals actually outline the original uncoded audiosignal of curve A. Since the signals of curves E and E are 180 out ofphase, timing sampler 70 to sample during positive peaks of the signalof curve E necessarily results in sampling during negative peaks of thesignal of curve E and produces a sampled version of the uncoded'audiosignal. Accordingly, generator 72 is phased by the line-drive pulses todevelop the sampling pulses of curve G for application to sampler 70,occurring at a 31.5 kilocycle rate and individually occurring in exacttime coincidence with the positive peaks of the sub-carrier shown incurve E. The composite signal of curve F is supplied to sampler 70wherein it is sampled or read at the occurrence of each pulse of curve Gand the sampler develops an output signal as shown in curve H. l

The signal of curve H is applied to low-passv lter 73 wherein it isshapedvto produce the signal ofVK curve l which is a simulation oftheoriginal uncoded audio signal of curve A and, of course, is related tothe coded audio signal of curveC. The signal of curve I is applied tospeaker 74 and the sound intelligence is reproduced without anyperceptible trace of transient distortion introduced as angincidentfftthe'decoding process or any distortion produced by -anabsence of theD.C. component. I if By way of summary, discriminator detector 62constitutesy demodulating means for Ademodulating the main sound carrierwave to derive the modulation components,` namely, `the A.C. componentand the D.C. modulated sub-carrier. Audio amplifier 63, phase splitter68, decoder 69 and source 38', collectively may be considered meanscoupled` to the demodulating means and responsive to the modulationcomponents for developing a coniposite signal (curve F) which is acombination of the subcarrier and the A.C. component. Generator 72 andsampler 70 constitute sampling means for effectively sarnpling onlycertain predetermined portions of the composite signal (namely, thepositive peaks of the subcarrier during the mode A intervals of curve Band the negative peaks of the sub-carrier during mode B intervals) todevelop an output signal (curve H) consisting of theV sampled portions.Finally, low-pass lter 73 constitutes frequency-selective means forshaping the Wave form of the output signal of curve H to form a signal(curve J) related to the intelligence signal of curve C represented bythe modulated main canier.

The invention, therefore, provides an improved` and simplified receiverfor reproducing a D.C. component. When incorporated in a subscriptiontelevision system, the arrangement prevents distortion in an audiosignal which has ben coded by phase inversion as explained whichdistortion normally arises due to the inability of the prior art systemsto reproduce and transmit the D.C. component of the coded signal. f

While a particular emboV ent of the' invention has been shown anddescribed, modifications may be made, and it is intended in the appendedclaims to cover all such modifications as may fall within the truespirit and scope of the invention.

1. A receiver for utilizing a main carrier wave which has been modulatedby a complex Wave form consisting of a sub-carrier signal representingthe unidirectional component of an intelligance signal conveying certaininformation and an alternating signal, representing the alternatingcomponent of said intelligence signal, added to said subcarrier signal,said receiver comprising:l demodulating means for demodulating said maincarrier wave to derive said complex wave form; means coupled to saiddemodulating means for phase inverting spacedfportions of said complexwaveform to develop a composite signall containing said sub-cam'ersignal as acomponent thereof; sampling means for effectively samplingsaid composite signal only at predetermined phase conditions of saidsubcarrier component to develop an output signal consisting of thesampled portions; and frequently-selective means for shaping the waveform of said output signal -to form a signal simulating saidinformation. 1

2. A receiver for utilizing a complex modulated main carrier waverepresenting an uncoded intelligence signal which has been subjected toa coding function and converted into a coded intelligence signal havingan alternating component and a unidirectional component which componentsare individually represented by separate modulations of said maincarrier wave, with the unidirectional component modulated on 'asub-carrier wave, said receiver comprising: demodulating means fordemodulating said main carrier Wave to derive a complex waveformcomprising said alternating component and the unidirectional modulatedsub-carrier signal; decoding apparatus coupled to said demodulatingmeans and responsiveto said complex waveform for performing a decodingfunction which is cornplementaryftoV said coding function to develop acomposite signal including a sub-carrier component having *was*predetermined phaseY conditions collectivelyl representing said uncodedintelligence signal; sampling means for effectively sampling onlysaidzpredetermined phase conditionsto develop an output signalconsisting. ofthegsampled portions; andfrequency-selective'means'forcshaping the Wave form of said outputsignalto simulate that of said uncoded intelligence signal.

3. A receiver for utilizing a complex modulated main carrier waverepresenting-.an uncoded intelligence signal which has been subjected tola-coding function and converted into a coded intelligence signal'havingan alternating component andfa unidirectional -lcomponentfwith theunidirectional component represented by a modulated sub-carrier signal,said receiver comprising: demodulating means for demodulating said mainIcarrier waveto derive said alternating component and the unidirectionalmodulated sub-carrier signal; 'decoding apparatus coupled to saiddemodulating means and responsive to said alternating component and theunidirectional modulated subcarrier signal for performing a decodingfunction which is complementary to said coding function to develop 'acomposite signal which is a combination of said subcarrier signal andsaid alternating component; sampling means for eectively sampling onlycertain predetermined phase conditions of the sub-carrier component ofsaid composite signal to develop an output signal consisting of thesampled portions; and frequency-selective means for shaping the waiveform of said output signal to form a simulation ofjsaid uncodedintelligence signal. V

4. A receiver for utilizing a complex modulated'main carrier Wavelrepresenting an uncoded audio signal which has been subjected to a phaseinverting coding function and converted into a coded audio signal havinga number of phase inversions occurring `in accordance with apredetermined code schedule-and having -an alternating component and aunidirectional component which components are individually representedby separate modulations of said main carrier wave, with theunidirectional component modulated on a sub-carrier signal, saidreceiver comprising: v,demodulating means for demodulating said maincarrier wave -to derive -a complex wave form comprising said alternatingcomponent and the unidirectional modulated sub-carrier signal; decodingapparatus coupled to said demodulating means for inverting the phase ofsaid complex Wave form at selected times determined by saidpredetermined code schedule to derive a composite signal including asub-carrier component` with certain amplitude peaks of the cycles of thesub-carrier component collectively representing said uncoded audiosignal; sampling means for effectively sampling only said certainamplitude peaks of the sub-carrier component of said composite signal todevelop an output signal consisting of the sampling portions; andfrequency-selective means for shaping the wave form of said outputsignal to simulate that of said uncoded audio signal.

5. A subscription television receiver for utilizing a televisiontransmission representing a video signal, a synchronizing signal, and anuncoded audio'signal which has been subjected to a coding function andconverted into `a coded audio signal having mode changes determined bysaid synchronizing signal and having an alternating component and aVunidirectional component which components are individually representedby separate modulations of said television transmission, with theunidirectional component modulated on a sub-carrier signal of saidtelevision transmission, said receiver comprising: demodulating meansfor deriving a complex wave form from said television transmissioncomprising said alternating component and the unidirectional modulatedsub-carrier signal; decoding apparatus coupled to said demodulatingmeans and responsive to said complex Wave form for performing a decodingfunction which is complementary to said coding function to develop acomposite signal including a sub-carrier component having predeterminedphase conditions collectively representing said uncoded audio signal;m'e'ans' for' derivingjsaid synchronizing signale'from Vs'aidgtcle'visontransmission; a sampling mechanism coupled-.to said synchronizingsignalderiving means and-operatedin synchronism-with said synchronizingsignalffor v.effectively sampling 4'only said predetermined phaseVconditions todevelop an outputsignal consisting of the sampled-portions;and frequency-selective means for shapin'gfthe Ywave forniofsaid-outputsignal to simulate that of said uncoded audio signal. V

. 6. A'rec'eiver forzutilizing acomplexmodulatedmain carrier Waverepresenting anluncoded audio signal'which has a characteristicathathas-,been varied-between la pluralityofrdifferent modes during a seriesof mode changingY intervals,`with the transitions between said -modessubject todntroducinggitransient distortion, and converted into a1 coded'audiocfsignal-Lhaving an alternating com-` ponentland aund-rectionalcomponent which components are individually representedr byA separatemodulations of said main carrier wave, said receiver comprising:demodulating means fordemodulating said main carrier wave Vto derivesaid separate modulations; decoding apparatus coupled to saiddemodulating means and responsive to said separate modulations forperforming a decoding function which is complementary to the codingfunction to which said uncoded audio signal has been subjected todevelop a composite signal having predetermined portions thereofoccurring at spaced time intervals different from said mode changingintervals and collectively representing said uncoded audio signal;sampling means for eifectively sampling only said predetermined portionsof said composite signal to develop anoutput signal consisting of thesampled portions; and frequency-selective means for shaping the waveform of said output signal to simulate that of said uncoded audiosignal.

7. A television receiver for utilizing a television transmissionrepresentinga video signal, a synchronizing signal and an uncoded audiosignal which has a characteristic that has been varied between aplurality of dierent modes during a series of mode changing intervalsdetermined by said synchronizing signal, with the transitions betweensaid mode subject to introducing transient distortion, and convertedinto a coded audio signal having an alternating component and aunidirectional component which components are individually representedby separate modulations of said Ktelevision transmission, said receivercomprising: demodulating means for demodulating said televisiontransmission to derive said separate modulations; decoding apparatuscoupled to said demodulating means and responsive to said separatemodulations for performing a decoding function which is complementary tothe coding function to which said uncoded audio signal has beensubjected to develop a composite signal having predetermined portions4thereof occurringV at spaced 'time intervals diierent from said modechanging intervals and collectively representing said uncoded audiosignal; means for deriving said synchronizing signal from saidtelevision transmission; a sampling mechanism coupled V- to saidsynchronizing signal deriving means and operated in synchronismwith'said synchronizing signal for eectively sampling only saidpredetermined portions of said composite signal to develop an outputsignal consisting Y of the'sampled portions; and frequency-selectivemeans for shaping the wave form of said output signal to simulate thatof said uncoded audio signal.

8. A television receiver for utilizing a television transmissionrepresenting a video signal, a held-synchronizing signal, aline-synchronizing signal, and an uncoded audio signal falling Within apredetermined frequency band which has been phase inverted during eachof a series of mode changing intervals in accordance with apredetermined code schedule and converted into a codedA audio signalhaving an alternating component and a unidirectional component with theunidirectional component represented by a modulated sub-carrier signalof said television transmission, said receiver comprising:demodusampling circuit' coupledi to said decoding apparatus; a l

pulsesignal source coupled to :said line-synchronizing deriving. meansfor supplying a pulsesignal tosaid `sampling circuit for effectingoperation .thereof at ya sampling frequency higher thantherupper-frequency of said predetermined band to *sample only said.ypredetermined portions of said composite'signal `todevelop an Outputsignal consisting ofthe sampled portions and also includinga samplingcomponent having a frequency corresponding-*to said lsamplingffrequency;and a low-pass filter for, effectively removing said sampling componentfrom said outputsignalto shape the wave form of said output signalrtosimulate that of said uncoded audio signal.

References Cited in the file of this patent vUNITED STATES PATENTSA2,567,545 Brown g,, Sept. 11, 1951 2,656,406 Gray et al. Oct. 20, 1953.2,664,460 Roschke De.29,1953 v2,677,721 Bedfqrd May 4, 1954 Y ivFRE-rcusi PATENTS, I

France n Apr. 15, 1953

